Furnace-regulator system



Mar. 27, 1923. 1,449,879.

C. A. BODDIE. FURNACE REGULATOR SYSTEM.

FILED APR.4. 1919.

WITNESSES:

lNVENTOR (/arewce A. Bodd/e W6. W641i ATTORNEY Patented Mar. 27, 1923.

UNITED STATES PATENT OFFICE.

CLARENCE A. BODDIE, 0F PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING-HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- SYLVANIA.

FURNACE-REGULATOR SYSTEM.

Application filed April 4, 1919. Serial No. 287,612.

To a]? whom it may concern Be it known that I, CLARENCE A. BoDmE, acitizen of th I nited States, and a resident of Pittsburgh, in thecounty of Allegheny and State of Pennsylvania, have invented a new anduseful Improvement in Furnace- Regulator Systems, of which the followingis a specification.

My invention relates to regulator systems and particularly to regulatorsystems for governing the operation of electric furnaces.

One object of my invention is to provide a furnace-regulator system thatshall be simple and effective in operation to maintain a fixed arebetween the movable electrode and the bath of material being treated andone that shall be provided with means for ensuring the regulator againstany so-called hunting action.

In an electric furnace of the movable-electrode type, it is necessary tokeep adjusting the electrode, relative to the bath of material beintreated, in order to maintain the power sup ilied to the furnacesubstantially constant. Adjustment of the electrode by hand isimpracticable, inasmuch as it requires the constant attention of anoperator to regulate such furnace and, moreover, it is diflicult toobtain satisfactory or close regulation of the furnace by such method.

Heretofore, the regulation or adjustment of the movable electrode hasbeenaccomplished by means of a regulator which is operative inaccordance with the current flowing through the furnace or in accordancewith the voltage obtaining between the movable electrode and the bath ofmaterial being treated. However, such operation has proven defective inmany cases by reason of failure to provide reliable and effective meansfor preventing a hunting action by the regulator.

In a furnace-regulator system constructed in accordance with myinvention, the movable electrode is raised and lowered, relative to thebath of material being treated, by means of a motor which is controlledby the current flowing through the furnace in a manner to preventovertravel or the socalled hunting action by it.

In detail, my regulator systemcomprises a main control electromagnetwhich is operated directly in accordance with the current flowingthrough the furnace and two switches which are governed by the maincontrol electromagnet. The two switches are provided with main switchmembers for operating the electrode motor in a forward and in a reversedirection in order to adjust the positioning of the movable electrode.The switches are further provided with interlock switch members forestablishing a braking circuit through the electrode motor upon releaseof the switches and with two interlock switch members for varying thenumber of effective turns in the winding of the main control magnet in amanner to prevent a hunting action by the regulator.

The two interlock switch members which control the number of effectiveturns included in the winding of the main control magnet arerespectively mounted on the two motor-controlling switches and increaseor decrease the number of effective turns in the winding of the. maincontrol magnet according to whether the movable electrode is beinglowered to increase the current-flow through the furnace or is beingraised to decrease the current-flow to the furnace. Thus, in case thecurrent flow through the furnace is above normal value, the main controlmagnet is energized for operating one of said main switches to effectrotative movement of the electrode motor in such direction that theelectrode is raised from the bath of material being treated to decreasethe currentflow through the furnace. Simultaneously with the operationof the electrode motor,

one of said interlock switch members is operated to short-circuit aportion of the Winding of the main control magnet and, accordingly, topermit the de-energization of the electrode motor just previous toobtaining normal current-flow in the furnace. Thus, the regulator isprevented from over-travelling and, if the furnace current is stillabove normal value, theabove operation is re eated.

Vhen the current-flow through the furnace is below normal value, thenthe number of effective turns included in the Winding of the maincontrol magnet is decreased upon actuation of the electrode motor, in-

asmuch as the electrodemotor, during such operation, is stopped byincreasing the energization of the main control electromagnet.

In the accompanying drawing, Figure 1 is a diagrammatic view of afurnace-regulator system constructed in accordance with my invention,and Fig. 2 is a modification of the furnace system illustrated in Fig.1.

Referring to Fig. 1 of the drawing, an electric furnace 1, comprising areceptacle 2 containing a bath of material 3 and a movable electrode 4,is connected to a supply circuit comprising conductors 5 and 6. Themovable electrode 4 is raised and lowered by a motor 7, comprising anarmature 8 and a field winding 9, in any suitable manner, as by aflexible-connector 10, a pulley 11 and a drum 12, which is rigidlymounted upon the armature shaft of the motor. The field winding 9 isconnected across a supply circuit comprising conductors 30 and 31.

A regulator 13 for operating the motor 7 in accordance with the currentflowing through thefurnace is provided, and comprises chiefly a maincontrol electric magnet 14 and two electrically operated switches 15 and16. The main control magnet 14 embodies an energizing coil 17, which isconnected to the supply conductor 6 by means of a current transformer18, and a core armature 19, the operation of which is adjusted by; meansof a dash-pot 20. The core armature 19 is pivotally connected to acontact arm 21 having main contact terminals 22 and 23 mounted on it.The two contact terminals are respectively moved to engage contactmembers 24 and 25 in accordance with the operation of the main contactmagnet. The energizing coil .17 of the magnet 14 is provided with threetaps 26, 27 and 28 extending therefrom for a purpose to be describedhereinafter.

The electrically operated switch 15 embodies an energizing coil 29 whichis connected across the supply conductors 30 and 31, by the engagementof the main contact members 23'and 25, and two main switch members 32and 33 which connect the motor 7 across the supply conductors 30 and 31for operating it in a counter-clockwise .direction to raise the member4. The switch 15 is further provided with two interlock switch members34 and 35. The interlock switch member 34- serves to short circuitsupply conductors 30 and 31 by the engagement of the main contactmembers 22 and 24, two main switch -mem'bers 37 and 38 which connect themotor 7 across the supply conductors 30 and 31 for rotating it in aclockwise direction to lower the electrode 4 and two interlock switchmembers 39 and 40. The interlock switch member 39 serves, upon operationof the switch 16, to open the short-circuit normally existing across thetaps 26 and 27 of the winding 17. The two interlock switch members 35and 40 serve to connect the supply conductors- 30 and 31 to a relay 41upon release of the two switches 15 and 16. The relay 41, uponoperation, completes a dynamic braking circuit for the motor 7 through aresistor 42.

In order to improve the operation of the main contact members, thewinding 29 of the switch 15, is shunted by a condenser 23 and aresistor'44, and the winding 36 of the switch 16 is shunted by thecondenser 45 and a resistor 46.

Assuming the system to be in the position shown in Fig. 1 and thecurrent-flow through the furnace 1 to be raised above normal value, thenthe main control magnet 14 is energized in a manner to connect the ber32, armature 8 of the motor 7 and the main switch member 33 to thesupply' conductor 31. Thus, the motor 7 is operated in acounter-clockwise direction to raise the electrode 4 from the bath ofmaterial 3 and to reduce the current flow through the furnace.

If the motor 7 were controlled solely by the effect upon the maincontrol magnet 14 of the current supplied to the furnace, the maincontrol magnet 14 would not be operated to stop the motor 7 until normalcur rent obtained in the supply conductors 5 and 6. Consequently, .byreason of the inertia of the various moving parts of the regulator, itis seen that the motor 7 would overtravel to raise the electrode 4beyond the desired point and, accordingly, to reduce the current-flow inthe furnace below normal value. In order to prevent such overtravel, theinterlock switch 34 is provided for changing the number of effectiveturns included in the winding-17 of the main controlmagnet 14.- Thus,when the switch 15 is operated, the interlock switch member 34short-circuits that portion of the winding 17 which is included betweenthe taps 27 and 28 and, consequently, the main control magnet 14 isoperated to separate the main contact members. 23 and 25 and stop themotor just previous to the obtaining of normal current-flow through thefurnace.

In case the current flow through the furnace drops below normal value,then the main control magnet 14 is operated to effect engagement betweenthe main contact members 22 and 24. Upon engagement of the contactmembers 22 and 24, a circuit is completed from the supply conductors 30and 31 through the energizing coil 36 of the switch 16. Thereupon, acircuit is completed from the supply conductors 30 and 31 through themain switch members 37 and 38 for operating the motor 7 in a clockwisedirection to effect a lowering of the electrode 4. Simultaneously withthe operation of the motor 7, the interlock switch member 39 opens theshort-circuit which existsacross the taps 26 and 27 of the winding 17 inorder to change the setting of the main control magnet 4 in a manner toprevent any hunting action by the regulator. Thus, just previous to theraising of the current-flow through the furnace to normal value bylowering the electrode 4, the main control magnet 14 is operated toefiect the separation of the main contact members 22 and 24. Thereupon,the

1 motor 7 is de-energized in a manner to prevent any overtravel by it.

It will be noted that at each operation of the motor 7, the twointerlock switches 35 and 40 serve to operate the relay 41 to comp-letea dynamic-braking circuit forefi'ecting a quick stopping of the motor.

in the modification illustrated in Fig. 2, parts corresponding to thoseshown in Fig. l are indicated by like reference characters, and only somuch of the system as difiers materially from the system shown in Fig. 1is illustrated.

Referring to Fig. 2, two electrically operated switches and 71 areprovided for operating the motor 7 in a manner somewhat similar to theoperation of the motor 7 by the switches 15 and 16. The switch 70 servesto connect the motor across the supply conductors 30 and 31 foroperating it in a counterclockwise direction .to raise the electrode ofthe furnace.

The switch 70 is provided with interlock switch members forshortcircuiting a portionof the winding 17 of the main control magnet 14and for establishing a braking circuit through the armature 8 upon thesimultaneous release of the two switches 70 and 71. The switch 71 servesto connect the motor 7 across the supply condoctors 30 and 31 to rotateit in a clockwise direction for effecting a lowering of the electrode.The switch 71 further is provided with interlock switch members foropening a short-circuit across a portion of the winding 17 of the maincontrol magnet 14 and for establishing a braking circuit through thearmature 8 upon the simultaneous release of the two switches.

The switch 70 embodies an energizing winding 72 which is connectedacross the supply conductors 30 and 31 by the engagement of the contactmembers 23 and 25, a core armature 73 which is pivotally connected to aswitch arm 74 and a holding coil 75 which is connected in series withthe motor armature. 8. The switch arm 74 is provided with an extension76 and an insulated interlock switch 77'which, respectively, serve toestablish a braking circuit through the armature 8 and a short circuitacross a portion of the winding 17, according to the position of theswitch arm 74. The holding coil 75 serves to hold the switch arm in areleased position.

The switch 71 embodies an energizing coil 79 which is connected acrossthe supply conductors 30 and 31 by the engagement of the contact members22 and 24, a core armature 80 which is pivotally connected to a contactarm 81 and a holding coil 82 which serves to maintain the switch arm 81in a released position upon de-energization of the energizing coil 79.The switch arm 81 is provided with an extension 83 and an interlockswitch member 84 which respectively serve to establish a dynamic-brakingcircuit through the armature 8 and to open a shortcircuit whichinitially exists across a portion of the winding 17 of the main controlmagnet 14.

In case the current flowing through the furnace is reduced below normalvalue, the main control magnet 14 is operated to engage the contactmembers 22 and 24. Upon engagement of the contact members 22 and 24, acircuit is completed for energizin the winding 79 to operate the switch71. T iereupon, a circuit is completed through the motor 7 which extendsfrom the supply conductor 31, through the switch arm 81, holding coil82, armature 8, holding coil 75 and the switch arm 74, to the supplyconductor 30. It will be noted that, upon operation of the switch 71,the interlock switch member 84 opens the short-circuit existing acrossthe taps 26 and 27 of the winding 17 in a manner exactly similar to theoperation of the interlock switch member '39 which is associated withthe electrically operated switch 16. Upon release of the switch 71, abraking circuit is completed which extends from one terminal of thearmature,8 through the holding coil 82, switch member 81, portion of thesupply conductor 30, switch arm 74 and the holding coil 75 to the otherterminal of the armature 8.

The switch 70 operates in ii similar manner upon an abnormalcurrent-flow through the furnace but, in this case, the interlock switchmember 77 serves to short-circuit a portion of the winding 17in a mannersimilar to the operation of the interlock switch member 34 which isoperated by the electrically operated switch 15.

Modifications in the system and arrangement and location of parts may bemade within the spirit and scope of my invention and such modificationsare intended to be covered bythe appended claims.

I claim as my invention:

1. In a regulator system, a sup-ply circuit, a main control magnethaving two operative positions, and means controlled, by said magnet,when in either of said operative positions, for varying the current flowthrough said cupply circuit and for simultaneously increasing ordecreasing the number of effective turns in the winding of said magnetto prevent hunting action.

2. In an electric furnace, the combination with an electrode motor, anda magnet operatedonly in accordance with the current flowing throughthevfurnace, of means controlled by said magnet for controlling theoperation of said motor, for varying the number of effective turns inthe winding of said magnet, and for establishing a motor braking circuitunder certain conditions.

3. In an electric furnace, an adjustable electrode, means for operatingsaid electrode, a main control electromagnet for governing the operationof said electrode-operating means, and means for varying the number ofeffective turns in the winding of said magnet to prevent hunting actionwhen the electrode is being lowered and raised.

- at. In an electric furnace, the combination with a movable electrode,a motor for operating said electrode, and a main control magnet operatedin accordance with the current flowing through the furnace, of meanscomprising twoswitches controlled by said main control magnet foroperating said motor in a forward and in a reverse direction, forincreasing or decreasing the number of effective turns in the winding ofsaid magnet to prevent a hunting action by the regulator, and forestablishing a braking circuit for said .motor when both ofsaid switchesare released.

5. In an electric furnace having an adjustable electrode, an electricmotor for op erating said electrode, switches for c'ontrolling thedirection of rotation of said motor, a main-control electromagnetoperated in ac cordance with the current flowing through the furnace,and means for varying the number of effective turns in the winding ofthe main-control magnet according to which of said switches is operatedto prevent hunting action during the raising and the lower-- ing of theelectrode.

6. In an electric furnace having an adjustable electrode, an electricmotor for rais-' action.

controlling the irection of rotation of said .motor, a main controlelectromagnet operated in accordance with the current passing throughthe furnace for selectively operating said switches, and meanscontrolled by said switches for simultaneously varying the energizationof the main-control magnet during the raising and the lowering operationof the'electrode.

7. In an electric furnace, the combination with a movable electrode anda motor for raising and lowering the electrode, of a magnet operated inaccordance with the current flowing through the electrode, meanscontrolled by said magnet for governing said motor and forsimultaneously varying the number of effective turns of said magnet toprevent hunting action during the raising-and the lowering of theelectrode.

8. In an electric furnace, the combination with a movable electrode, andmeans for operating said electrode, of a main control electromagnetoperated in accordance with the current flowing through the furnace, andmeans controlled b said magnet for governing said electro e-operatingmeans and for simultaneously selectively increasing or decreasing thenumber of effective turns in the windings of saidmagnet according towhether said electrode is being lowered or raised.

9. In an electric furnace, an adjustable electrode, means for raisingand lowering said electrode, a magnet for governing the operation ofsaid means, and means for selectively varying the energization of saidmagnet to prevent hunting action during the raising and the lowering 9fthe electrode;

10. In an electric furnace, a movable electrode, means for raising andlowering said electrode, a magnet operated in accordance with thecurrent flowing through the furnace for controlling said means, andmeans for automatically'opposing the initial operation of saidmagnetwhen the electrode is being raised or lowered to prevent hunting11. In an electric furnace, a movable electrode, means for raising andlowering said electrode in accordance with furnace conditions, andauxiliary means controlled by said first-mentioned means and serving t9automatically oppose its initial operation.

In testimony whereof, I have hereunto subscribed my name this 25thMarch, 1919.

CLARENCE A. BODDIE.

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